He was not the one accused of human organ trafficking, nor the money-laundering rabbi. No, in the sprawling corruption sting that shook New Jersey last year, what marked Peter J. Cammarano III, then the mayor of Hoboken, was the spectacle of a promising career blown apart almost before it started.

His downfall became complete on Tuesday, in Federal District Court in Newark, where Mr. Cammarano, 32, pleaded guilty to accepting illegal campaign contributions in return for aiding proposed development projects. The youngest mayor in the city’s history, he served 23 days in that office last year before being arrested and charged, and eight more before resigning. He now faces a probable sentence of 24 to 30 months in prison.

“This is really a sad day for Hoboken,” Dawn Zimmer, who succeeded Mr. Cammarano as mayor, lamented on Tuesday afternoon. “It’s sad to be on the map for corruption again. We don’t want to be known for this.”

A lawyer who ran on a platform of fiscal responsibility, Mr. Cammarano was once called a rising star in the Democratic Party. But he turned out to be just one in a distressingly long list of government officials whose allegiances and official favors were for sale. (A predecessor as mayor, Anthony Russo, pleaded guilty in a corruption case in 2004.)

Last summer, the United States attorney’s office in Newark unveiled what officials called the biggest corruption sweep in the state’s history, charging 44 people across multiple counties, including three mayors, two state lawmakers, a deputy mayor of Jersey City, assorted other government officials and political operatives and a group of rabbis. Mr. Cammarano, one of the most prominent defendants, was the 17th to plead guilty; one other, Leona Beldini, the former Jersey City deputy mayor, was convicted at trial.

The breadth of the case and its baroque details made it a staple of late-night television comedy shows, piling on New Jersey’s well-established reputation for official vice. Christopher J. Christie, a former prosecutor, exploited the sting in his successful campaign for governor last year.

Mr. Cammarano appeared before Judge Jose L. Linares in a blue striped suit and pleaded guilty to one count of “conspiracy to commit extortion under color of official right,” then left the courthouse without speaking to reporters. He admitted that he took $25,000 in illicit campaign contributions in return for promises to help a developer, who was actually working for the Federal Bureau of Investigation.

The donations came during and just after Mr. Cammarano’s hard-fought mayoral campaign, including a runoff in which he narrowly defeated Ms. Zimmer. As City Council president, she became acting mayor when he resigned, and then won a special election and become mayor in her own right in November.

Mr. Cammarano remains free pending sentencing on Aug. 3.

“Peter Cammarano has accepted responsibility for his conduct,” said his lawyer, Joseph A. Hayden Jr. “He is only 32 years old, and after the criminal process is completed, he will rebuild his life as a productive member of society.”

Paul J. Fishman, the United States attorney for New Jersey, said Mr. Cammarano had “sold his influence,” and in that regard was no different from countless other corrupt officials before him.

“I’m disappointed that this issue doesn’t go away,” Mr. Fishman said in an interview. “I would hope that all public officials would understand that their job involves a public trust, and that they shouldn’t attempt to feather their own nests at the expense of the constituents they are sworn to serve. Unfortunately, there are some number of folks who haven’t gotten that message.”

The common thread in last year’s corruption sweep was Solomon Dwek, a one-time real estate developer who was, himself, caught in illegal financial dealings, and became a cooperating witness. He offered bundles of cash in return for support for fictitious projects, and apparently had no trouble finding takers. Some took illicit campaign contributions, others pocketed the money, prosecutors say.

The case snared defendants from New Jersey and New York, including several rabbis accused of running a money-laundering ring and a man accused of trying to arrange the illegal sale of a human kidney.